Enlarged cell size foams made from blends of alkenyl aromatic polymers and alpha-olefin/vinyl or vinylidene aromatic and/or sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene interpolymers

ABSTRACT

This invention pertains to a composition and a process for preparing a closed cell alkenyl aromatic polymer foam having enlarged cell size, comprising one or more alkenyl aromatic polymers, one or more substantially random interpolymers, one or more blowing agents having zero ozone depletion potential and optionally one or more co-blowing agents, and optionally, one or more nucleating agents and optionally, one or more other additives. 
     This combination allows the manufacture of closed cell, low density alkenyl aromatic polymer foams of enlarged cell size, when blowing agents of relatively high nucleation potential are employed. When such blowing agents are used with alkenyl aromatic polymers in the absence of the substantially random interpolymers, small cell foams result.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

FIELD OF THE INVENTION

This invention describes a method for enlarging cell sizes of alkenylaromatic foams by blending polymers which comprise; (A) alkenyl aromaticpolymers, and (B) vinyl or vinylidene aromatic and/or stericallyhindered aliphatic or cycloaliphatic vinyl or vinylidene substantiallyrandom interpolymers. Suitable alkenyl aromatic polymers include alkenylaromatic homopolymers and copolymers of alkenyl aromatic compounds andcopolymerizable ethylenically unsaturated comonomers. The alkenylaromatic polymer material comprises greater than 50 and preferablygreater than 70 weight percent alkenyl aromatic monomeric units. Mostpreferably, the alkenyl aromatic polymer material is comprised entirelyof alkenyl aromatic monomeric units. Suitable alkenyl aromatic polymersinclude those derived from alkenyl aromatic compounds such as styrene,alpha-methylstyrene, etc. A preferred alkenyl aromatic polymer ispolystyrene. Examples of copolymerizable compounds include acrylic acid,methacrylic acid, acrylonitrile, etc. The substantially randominterpolymers comprise polymer units derived from ethylene and/or one ormore α-olefin monomers with specific amounts of one or more vinyl orvinylidene aromatic monomers and/or sterically hindered aliphatic orcycloaliphatic vinyl or vinylidene monomers. A preferred substantiallyrandom interpolymer is an ethylene/styrene interpolymer. Incorporationof the substantially random interpolymer in the blend with the alkenylaromatic polymer allows the formation of foams having enlarged cellsizes when blowing agents of reduced or zero ozone-depletion potential(which have low solubility and relatively high nucleation potential) areemployed.

BACKGROUND OF THE INVENTION

Due to present environmental concerns over the use of ozone-depletingblowing agents, it is desirable to make alkenyl aromatic polymer foamswith blowing agents having reduced or zero ozone-depletion potential.Such blowing agents include inorganic blowing agents such as nitrogen,sulfur hexafluoride (SF₆), and argon; organic blowing agents such ascarbon dioxide and hydrofluorocarbons such as 1,1,1,2-tetrafluoroethane(HFC-134a), 1,1,2,2-tetrafluoroethane (HFC-134),1,1,1,3,3-pentafluoropropane, difluoromethane (HFC-32),1,1-difluoroethane (HFC-152a), pentafluoroethane (HFC-125), fluoroethane(HFC-161) and 1,1,1-trifluoroethane (HFC-143a) and hydrocarbons such asmethane, ethane, propane, n-butane, isobutane, n-pentane, isopentane,cyclopentane and neopentane; and chemical blowing agents which includeazodicarbonamide, azodiisobutyro-nitrile, benzenesulfonylhydrazide,4,4-oxybenzene sulfonyl-semicarbazide, p-toluene sulfonylsemi-carbazide, barium azodicarboxylate,N,N'-dimethyl-N,N'-dinitrosoterephthalamide, trihydrazino triazine andmixtures of citric acid and sodium bicarbonate such as the variousproducts sold under the name Hydrocerol™ (a product and trademark ofBoehringer Ingelheim). All of these blowing agents may be used as singlecomponents or any mixture in combination thereof, or in mixtures withother co-blowing agents.

A problem with using the above non ozone-depleting blowing agents istheir tendency to form foams of relatively small cell size andcross-section. Such blowing agents typically result in foams havingsmall cell sizes due to their relatively high nucleation potential.Small cell size is especially a problem when particular infraredattenuating agents are employed such as carbon black, graphite, andtitanium dioxide.

It would be desirable to be able to employ the non-ozone depletingblowing agents in making alkenyl aromatic polymer foams with or withoutinfrared attenuating agents yet be able to enlarge the cell size of thefoam. Enlarging the cell size of the foams would enable greaterthicknesses and larger cross-sectional areas to be obtained, as well asafford a reduction in foam density in some cases. Lower foam densitieswould be desirable for both extruded and expanded alkenyl aromaticpolymer foams. Greater foam thicknesses and cross-sections would enablea broader range of products to be manufactured, and reducing densitywould allow foams to be manufactured more economically. It is alsodesirable for the foams to exhibit acceptable physical properties.

Prior art attempts to make a foam having enlarged cell size include theintegration of a wax in a foam forming gel prior to extrusion of the gelthrough a die to form a foam. Such use of a wax is seen in U.S. Pat. No.4,229,396, which is incorporated herein by reference. The use of a waxmay however, present processing problems and cause thermal stabilityvariations or diminution in physical properties in product foams. Thewax may also cause inconsistency in extrusion temperatures. Additionalprior art attempts to make a foam having enlarged cell size include theincorporation of a non-waxy compound in a foam forming gel prior toextrusion of the gel through a die to form a foam. Such use of anon-waxy compound is seen in U.S. Pat. No. 5,489,407, which isincorporated herein by reference. Large cell size alkenyl aromaticpolymer foams have been prepared using glycerol monoesters of C₈ -C₂₄fatty acids as cell size enlarging agents as disclosed in U.S. Pat. No.5,776,389, the entire contents of which are incorporated herein byreference. However the concentration of such agents in a foam that canbe used is limited, as high levels depress the glass transitiontemperature of the polymer and can result in degradation of physicalproperties such as creep under load (at 80° C.).

Thus it would be desirable to identify cell size enlarging compoundswhich can be used in conjunction with non-ozone depleting blowing agentsand do not have an adverse effect on the physical or mechanicalproperties of the foam.

BRIEF SUMMARY OF THE INVENTION

The present invention pertains to improved closed cell alkenyl aromaticpolymer foams having enlarged cell size, comprising;

(A) from about 80 to about 99.7 percent by weight (based on the combinedweight of Components A and B) of one or more alkenyl aromatic polymers,and wherein at least one of said alkenyl aromatic polymers has amolecular weight (M_(w)) of from about 100,000 to about 500,000; and

(B) from about 0.3 to about 20 percent by weight (based on the combinedweight of Components A and B) of one or more substantially randominterpolymers having an I₂ of about 0.01 to about 1000 g/10 min, and anM_(w) /M_(n) of about 1.5 to about 20; comprising;

(1) from about 8 to about 65 mol % of polymer units derived from;

(a) at least one vinyl or vinylidene aromatic monomer, or

(b) at least one hindered aliphatic or cycloaliphatic vinyl orvinylidene monomer, or

(c) a combination of at least one aromatic vinyl or vinylidene monomerand at least one hindered aliphatic or cycloaliphatic vinyl orvinylidene monomer, and

(2) from about 35 to about 92 mol % of polymer units derived from atleast one of ethylene and/or a C₃₋₂₀ α-olefin; and

(3) from 0 to about 20 mol % of polymer units derived from one or moreof ethylenically unsaturated polymerizable monomers other than thosederived from (1) and (2); and

(C) optionally, one or more nucleating agents and

(D) optionally, one or more other additives; and

(E) one or more blowing agents having zero ozone depletion potentialand, optionally one or more co-blowing agents, present in a total amountof from about 0.2 to about 5.0 g moles per kg (based on the combinedweight of Components A and B); wherein

the cell size of said foam is enlarged about 5 percent or more relativeto a corresponding foam without the substantially random interpolymer.

This combination allows the manufacture of low density alkenyl aromaticpolymer foams of enlarged cell size and relatively thick cross-section,when blowing agents of relatively high nucleation potential areemployed. When these blowing agents are used with alkenyl aromaticpolymer in the absence of the substantially random interpolymers, smallcell foams result. In addition, we have unexpectedly found that cellsize can be enlarged by using substantially random interpolymers withouta substantial degradation of foam mechanical properties (as occurs ifhigh concentrations of prior art cell size enlargers such as glycerolmonoesters are used). Furthermore foam density can be decreased in somecases, which is desirable for both extruded and expanded foams made fromalkenyl aromatic polymers.

Definitions

All references herein to elements or metals belonging to a certain Grouprefer to the Periodic Table of the Elements published and copyrighted byCRC Press, Inc., 1989. Also any reference to the Group or Groups shallbe to the Group or Groups as reflected in this Periodic Table of theElements using the IUPAC system for numbering groups.

Any numerical values recited herein include all values from the lowervalue to the upper value in increments of one unit provided that thereis a separation of at least 2 units between any lower value and anyhigher value. As an example, if it is stated that the amount of acomponent or a value of a process variable such as, for example,temperature, pressure, time and the like is, for example, from 1 to 90,preferably from 20 to 80, more preferably from 30 to 70, it is intendedthat values such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 etc. areexpressly enumerated in this specification. For values which are lessthan one, one unit is considered to be 0.0001, 0.001, 0.01 or 0.1 asappropriate. These are only examples of what is specifically intendedand all possible combinations of numerical values between the lowestvalue and the highest value enumerated are to be considered to beexpressly stated in this application in a similar manner.

The term "hydrocarbyl" as employed herein means any aliphatic,cycloaliphatic, aromatic, aryl substituted aliphatic, aryl substitutedcycloaliphatic, aliphatic substituted aromatic, or aliphatic substitutedcycloaliphatic groups.

The term "hydrocarbyloxy" means a hydrocarbyl group having an oxygenlinkage between it and the carbon atom to which it is attached.

The term "copolymer" as employed herein means a polymer wherein at leasttwo different monomers are polymerized to form the copolymer.

The term "interpolymer" is used herein to indicate a polymer wherein atleast two different monomers are polymerized to make the interpolymer.This includes copolymers, terpolymers, etc. iThe term "enlarged cellsize" is used herein to indicate a foam having an increase of cell sizeof about 5%, preferably about 10%, more preferably about 15% or morerelative to an analogous foam made without the substantially randominterpolymer.

DETAILED DESCRIPTION OF THE INVENTION

The invention especially covers foams comprising blends of one or morealkenyl aromatic homopolymers, or copolymers of alkenyl aromaticmonomers, and/or copolymers of alkenyl aromatic monomers with one ormore copolymerizeable ethylenically unsaturated comonomers (other thanethylene or linear C₃ -C,₁₂ α-olefins) with at least one substantiallyrandom interpolymer. The foams of this invention have enlarged cellsizes relative to corresponding foams of similar density made withoutthe substantially random interpolymer.

The alkenyl aromatic polymer material may further include minorproportions of non-alkenyl aromatic polymers. The alkenyl aromaticpolymer material may be comprised solely of one or more alkenyl aromatichomopolymers, one or more alkenyl aromatic copolymers, a blend of one ormore of each of alkenyl aromatic homopolymers and copolymers, or blendsof any of the foregoing with a non-alkenyl aromatic polymer. Regardlessof composition, the alkenyl aromatic polymer material comprises greaterthan 50 and preferably greater than 70 weight percent alkenyl aromaticmonomeric units. Most preferably, the alkenyl aromatic polymer materialis comprised entirely of alkenyl aromatic monomeric units.

Suitable alkenyl aromatic polymers include homopolymers and copolymersderived from alkenyl aromatic compounds such as styrene,alphamethylstyrene, ethylstyrene, vinyl benzene, vinyl toluene,chlorostyrene, and bromostyrene. A preferred alkenyl aromatic polymer ispolystyrene. Minor amounts of monoethylenically unsaturated compoundssuch as C₂₋₆ alkyl acids and esters, ionomeric derivatives, and C₄₋₆dienes may be copolymerized with alkenyl aromatic compounds. Examples ofcopolymerizable compounds include acrylic acid, methacrylic acid,ethacrylic acid, maleic acid, itaconic acid, acrylonitrile, maleicanhydride, methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butylacrylate, methyl methacrylate, vinyl acetate and butadiene.

The term "substantially random" (in the substantially randominterpolymer comprising polymer units derived from ethylene and one ormore α-olefin monomers with one or more vinyl or vinylidene aromaticmonomers and/or aliphatic or cycloaliphatic vinyl or vinylidenemonomers) as used herein means that the distribution of the monomers ofsaid interpolymer can be described by the Bernoulli statistical model orby a first or second order Markovian statistical model, as described byJ. C. Randall in POLYMER SEQUENCE DETERMINATION Carbon- 13 NMR Method,Academic Press New York, 1977, pp. 71-78. Preferably, substantiallyrandom interpolymers do not contain more than 15 percent of the totalamount of vinyl aromatic monomer in blocks of vinyl aromatic monomer ofmore than 3 units. More preferably, the interpolymer is notcharacterized by a high degree of either isotacticity orsyndiotacticity. This means that in the carbon⁻¹³ NMR spectrum of thesubstantially random interpolymer the peak areas corresponding to themain chain methylene and methine carbons representing either meso diadsequences or racemic diad sequences should not exceed 75 percent of thetotal peak area of the main chain methylene and methine carbons.

The interpolymers used to prepare the foams of the present inventioninclude the substantially random interpolymers prepared by polymerizingi) ethylene and/or one or more α-olefin monomers and ii) one or morevinyl or vinylidene aromatic monomers and/or one or more stericallyhindered aliphatic or cycloaliphatic vinyl or vinylidene monomers, andoptionally iii) other polymerizable ethylenically unsaturatedmonomer(s). Suitable α-olefins include for example, α-olefins containingfrom 3 to about 20, preferably from 3 to about 12, more preferably from3 to about 8 carbon atoms. Particularly suitable are ethylene,propylene, butene-1, 4-methyl-1-pentene, hexene-1 or octene-1 orethylene in combination with one or more of propylene, butene-1,4-methyl-1-pentene, hexene-1 or octene-1. These α-olefins do not containan aromatic moiety.

Other optional polymerizable ethylenically unsaturated monomer(s)include norbornene and C₁₋₁₀ alkyl or C₆₋₁₀ aryl substitutednorbornenes, with an exemplary interpolymer beingethylene/styrene/norbomene.

Suitable vinyl or vinylidene aromatic monomers which can be employed toprepare the interpolymers include, for example, those represented by thefollowing formula: ##STR1## wherein R¹ is selected from the group ofradicals consisting of hydrogen and alkyl radicals containing from 1 toabout 4 carbon atoms, preferably hydrogen or methyl; each R² isindependently selected from the group of radicals consisting of hydrogenand alkyl radicals containing from 1 to about 4 carbon atoms, preferablyhydrogen or methyl; Ar is a phenyl group or a phenyl group substitutedwith from 1 to 5 substituents selected from the group consisting ofhalo, C₁₋₄ -alkyl, and C₁₋₄ -haloalkyl; and n has a value from zero toabout 4, preferably from zero to 2, most preferably zero. Exemplaryvinyl aromatic monomers include styrene, vinyl toluene, α-methylstyrene,t-butyl styrene, chlorostyrene, including all isomers of thesecompounds, and the like. Particularly suitable such monomers includestyrene and lower alkyl- or halogen-substituted derivatives thereof.Preferred monomers include styrene, α-methyl styrene, the loweralkyl-(C₁ -C₄) or phenyl-ring substituted derivatives of styrene, suchas for example, ortho-, meta-, and para-methylstyrene, the ringhalogenated styrenes, para-vinyl toluene or mixtures thereof, and thelike. A more preferred aromatic vinyl monomer is styrene.

By the term "sterically hindered aliphatic or cycloaliphatic vinyl orvinylidene compounds", it is meant addition polymerizable vinyl orvinylidene monomers corresponding to the formula: ##STR2## wherein A¹ isa sterically bulky, aliphatic or cycloaliphatic substituent of up to 20carbons, R¹ is selected from the group of radicals consisting ofhydrogen and alkyl radicals containing from 1 to about 4 carbon atoms,preferably hydrogen or methyl; each R² is independently selected fromthe group of radicals consisting of hydrogen and alkyl radicalscontaining from 1 to about 4 carbon atoms, preferably hydrogen ormethyl; or alternatively R¹ and A¹ together form a ring system.Preferred aliphatic or cycloaliphatic vinyl or vinylidene compounds aremonomers in which one of the carbon atoms bearing ethylenic unsaturationis tertiary or quaternary substituted. Examples of such substituentsinclude cyclic aliphatic groups such as cyclohexyl, cyclohexenyl,cyclooctenyl, or ring alkyl or aryl substituted derivatives thereof,tert-butyl, norbornyl, and the like. Most preferred aliphatic orcycloaliphatic vinyl or vinylidene compounds are the various isomericvinyl- ring substituted derivatives of cyclohexene and substitutedcyclohexenes, and 5-ethylidene-2-norbornene. Especially suitable are 1-,3-, and 4-vinylcyclohexene. Simple linear non-branched α-olefinsincluding for example, α-olefins containing from 3 to about 20 carbonatoms such as propylene, butene-1, 4-methyl-1-pentene, hexene-1 oroctene-1 are not examples of sterically hindered aliphatic orcycloaliphatic vinyl or vinylidene compounds.

One method of preparation of the substantially random interpolymersincludes polymerizing a mixture of polymerizable monomers in thepresence of one or more metallocene or constrained geometry catalysts incombination with various cocatalysts, as described in EP-A-0,416,815 byJames C. Stevens et al. and U.S. Pat. No. 5,703,187 by Francis J.Timmers, both of which are incorporated herein by reference in theirentirety. Preferred operating conditions for such polymerizationreactions are pressures from atmospheric up to 3000 atmospheres andtemperatures from -30° C. to 200° C. Polymerizations and unreactedmonomer removal at temperatures above the autopolymerization temperatureof the respective monomers may result in formation of some amounts ofhomopolymer polymerization products resulting from free radicalpolymerization.

Examples of suitable catalysts and methods for preparing thesubstantially random interpolymers are disclosed in U.S. applicationSer. No. 702,475, filed May 20, 1991 (EP-A-514,828); as well as U.S.Pat. Nos. 5,055,438; 5,057,475; 5,096,867; 5,064,802; 5,132,380;5,189,192; 5,321,106; 5,347,024; 5,350,723; 5,374,696; 5,399,635;5,470,993; 5,703,187; and 5,721,185 all of which patents andapplications are incorporated herein by reference.

The substantially random (α-olefin/vinyl aromatic interpolymers can alsobe prepared by the methods described in JP 07/278230 employing compoundsshown by the general formula ##STR3## where Cp¹ and Cp² arecyclopentadienyl groups, indenyl groups, fluorenyl groups, orsubstituents of these, independently of each other; R¹ and R² arehydrogen atoms, halogen atoms, hydrocarbon groups with carbon numbers of1-12, alkoxyl groups, or aryloxyl groups, independently of each other; Mis a group IV metal, preferably Zr or Hf, most preferably Zr; and R³ isan alkylene group or silanediyl group used to cross-link Cp¹ and Cp²).

The substantially random α-olefin/vinyl aromatic interpolymers can alsobe prepared by the methods described by John G. Bradfute et al. (W. R.Grace & Co.) in WO 95/32095; by R. B. Pannell (Exxon Chemical Patents,Inc.) in WO 94/00500; and in Plastics Technology, p. 25 (September1992), all of which are incorporated herein by reference in theirentirety.

Also suitable are the substantially random interpolymers which compriseat least one α-olefin/vinyl aromatic/vinyl aromatic/α-olefin tetraddisclosed in U. S. application Ser. No. 08/708,869 filed Sep. 4, 1996and WO 98/09999 both by Francis J. Timmers et al. These interpolymerscontain additional signals in their carbon-13 NMR spectra withintensities greater than three times the peak to peak noise. Thesesignals appear in the chemical shift range 43.70-44.25 ppm and 38.0-38.5ppm. Specifically, major peaks are observed at 44.1, 43.9, and 38.2 ppm.A proton test NMR experiment indicates that the signals in the chemicalshift region 43.70 -44.25 ppm are methine carbons and the signals in theregion 38.0-38.5 ppm are methylene carbons.

It is believed that these new signals are due to sequences involving twohead-to-tail vinyl aromatic monomer insertions preceded and followed byat least one α-olefin insertion, e.g. anethylene/styrene/styrene/ethylene tetrad wherein the styrene monomerinsertions of said tetrads occur exclusively in a 1,2 (head to tail)manner. It is understood by one skilled in the art that for such tetradsinvolving a vinyl aromatic monomer other than styrene and an α-olefinother than ethylene that the ethylene/vinyl aromatic monomer/vinylaromatic monomer/ethylene tetrad will give rise to similar carbon-13 NMRpeaks but with slightly different chemical shifts.

These interpolymers can be prepared by conducting the polymerization attemperatures of from about -30° C. to about 250° C. in the presence ofsuch catalysts as those represented by the formula ##STR4## wherein:each Cp is independently, each occurrence, a substitutedcyclopentadienyl group π-bound to M; E is C or Si; M is a group IVmetal, preferably Zr or Hf, most preferably Zr; each R is independently,each occurrence, H, hydrocarbyl, silahydrocarbyl, or hydrocarbylsilyl,containing up to about 30 preferably from 1 to about 20 more preferablyfrom 1 to about 10 carbon or silicon atoms; each R' is independently,each occurrence, H, halo, hydrocarbyl, hyrocarbyloxy, silahydrocarbyl,hydrocarbylsilyl containing up to about 30 preferably from 1 to about 20more preferably from 1 to about 10 carbon or silicon atoms or two R'groups together can be a C₁₋₁₀ hydrocarbyl substituted 1,3-butadiene; mis 1 or 2; and optionally, but preferably in the presence of anactivating cocatalyst. Particularly, suitable substitutedcyclopentadienyl groups include those illustrated by the formula:##STR5## wherein each R is independently, each occurrence, H,hydrocarbyl, silahydrocarbyl, or hydrocarbylsilyl, containing up toabout 30 preferably from 1 to about 20 more preferably from 1 to about10 carbon or silicon atoms or two R groups together form a divalentderivative of such group. Preferably, R independently each occurrence is(including where appropriate all isomers) hydrogen, methyl, ethyl,propyl, butyl, pentyl, hexyl, benzyl, phenyl or silyl or (whereappropriate) two such R groups are linked together forming a fused ringsystem such as indenyl, fluorenyl, tetrahydroindenyl,tetrahydrofluorenyl, or octahydrofluorenyl.

Particularly preferred catalysts include, for example,racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl) zirconiumdichloride, racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl)zirconium 1,4-diphenyl-1,3-butadiene,racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl) zirconiumdi-C1-4 alkyl,racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl) zirconiumdi-C1 -4 alkoxide, or any combination thereof and the like.

It is also possible to use the following titanium-based constrainedgeometry catalysts, [N-(1,1-dimethylethyl)-1,1-dimethyl-1-[(1,2,3,4,5-η)-1, 5,6,7-tetrahydro-s-indacen-1-yl]silanaminato(2-)-N]titaniumdimethyl; (1-indenyl)(tert-butylamido)-dimethylsilane titanium dimethyl;((3-tert-butyl)(1,2,3,4,5-η)-1-indenyl)(tert-butylamido) dimethylsilanetitanium dimethyl; and ((3-iso-propyl)(1,2,3,4,5-η)-1-indenyl)(tert-butyl amido)dimethylsilane titanium dimethyl, or any combinationthereof and the like.

Further preparative methods for the interpolymers used in the presentinvention have been described in the literature. Longo and Grassi(Makromol. Chem., Volume 191, pages 2387 to 2396 [1990]) and D'Annielloet al. (Journal of Applied Polymer Science, Volume 58, pages 1701-1706[1995]) reported the use of a catalytic system based on methylalumoxane(MAO) and cyclopentadienyltitanium trichloride (CpTiCl₃) to prepare anethylene-styrene copolymer. Xu and Lin (Polymer Preprints, Am. Chem.Soc., Div. Polym. Chem.) Volume 35, pages 686,687 [1994]) have reportedcopolymerization using a MgCl₂ /TiCl₄ /NdCl₃ /Al(iBu)₃ catalyst to giverandom copolymers of styrene and propylene. Lu et al (Journal of AppliedPolymer Science, Volume 53, pages 1453 to 1460 [1994]) have describedthe copolymerization of ethylene and styrene using a TiCl₄ /NdCl₃ /MgCl₂/Al(Et)₃ catalyst. Sernetz and Mulhaupt, (Macromol. Chem. Phys., v. 197,pp. 1071-1083, 1997) have described the influence of polymerizationconditions on the copolymerization of styrene with ethylene using Me₂Si(Me₄ Cp)(N-tert-butyl)TiCl₂ /methylaluminoxane Ziegler-Nattacatalysts. Copolymers of ethylene and styrene produced by bridgedmetallocene catalysts have been described by Arai, Toshiaki and Suzuki(Polymer Preprints, Am. Chem. Soc., Div. Polym. Chem.) Volume 38, pages349, 350 [1997]) and in U.S. Pat. No. 5,652,315, issued to Mitsui ToatsuChemicals, Inc. The manufacture of aα-olefin/vinyl aromatic monomerinterpolymers such as propylene/styrene and butene/styrene are describedin U.S. Pat. No. 5,244,996, issued to Mitsui Petrochemical IndustriesLtd or U.S. Pat. No. 5,652,315 also issued to Mitsui PetrochemicalIndustries Ltd or as disclosed in DE 197 11 339 A1 to Denki Kagaku KogyoKK. All the above methods disclosed for preparing the interpolymercomponent are incorporated herein by reference. The random copolymers ofethylene and styrene as disclosed in Polymer Preprints Vol 39, No. 1,March 1998 by Toru Aria et al. can also be employed as blend componentsfor the foams of the present invention.

While preparing the substantially random interpolymer, an amount ofatactic vinyl aromatic homopolymer may be formed due tohomopolymerization of the vinyl aromatic monomer at elevatedtemperatures. The presence of vinyl aromatic homopolymer is in generalnot detrimental for the purposes of the present invention and can betolerated. The vinyl aromatic homopolymer may be separated from theinterpolymer, if desired, by extraction techniques such as selectiveprecipitation from solution with a non solvent for either theinterpolymer or the vinyl aromatic homopolymer. For the purpose of thepresent invention it is preferred that no more than 30 weight percent,preferably less than 20 weight percent based on the total weight of theinterpolymers of atactic vinyl aromatic homopolymer is present.

Preparation of the Foams of the Present Invention

The compositions of the present invention may be used to form extrudedthermoplastic polymer foam, expandable thermoplastic foam beads orexpanded thermoplastic foams, and molded articles formed by expansionand/or coalescing and welding of those particles.

The foams may take any known physical configuration, such as extrudedsheet, rod, plank, films and profiles. The foam structure also may beformed by molding expandable beads into any of the foregoingconfigurations or any other configuration.

Foam structures may be made by a conventional extrusion foaming process.The present foam is generally prepared by melt blending in which thealkenyl aromatic polymer material and one or more substantially randominterpolymers are heated together to form a plasticized or melt polymermaterial, incorporating therein a blowing agent to form a foamable gel,and extruding the gel through a die to form the foam product. Prior toextruding from the die, the gel is cooled to an optimum temperature. Tomake a foam, the optimum temperature is at or above the blends glasstransition temperature or melting point. For the foams of the presentinvention the optimum foaming temperature is in a range sufficient toproduce an open cell content in the foam of 20 vol % or less and tooptimize physical characeristics of the foam structure. The blowingagent may be incorporated or mixed into the melt polymer material by anymeans known in the art such as with an extruder, mixer, blender, or thelike. The blowing agent is mixed with the melt polymer material at anelevated pressure sufficient to prevent substantial expansion of themelt polymer material and to generally disperse the blowing agenthomogeneously therein. Optionally, a nucleator may be blended in thepolymer melt or dry blended with the polymer material prior toplasticizing or melting. The substantially random interpolymers may bedry-blended with the polymer material prior to charging to the extruder,or charged to the extruder in the form of a polymer concentrate or ainterpolymer/color pigment carrier material. The foamable gel istypically cooled to a lower temperature to optimize physicalcharacteristics of the foam structure. The gel may be cooled in theextruder or other mixing device or in separate coolers. The gel is thenextruded or conveyed through a die of desired shape to a zone of reducedor lower pressure to form the foam structure. The zone of lower pressureis at a pressure lower than that in which the formable gel is maintainedprior to extrusion through the die. The lower pressure may besuperatmospheric or subatmospheric (vacuum), but is preferably at anatmospheric level.

The present foam structures may be formed in a coalesced strand form byextrusion of the compositions of the present invention through amulti-orifice die. The orifices are arranged so that contact betweenadjacent streams of the molten extrudate occurs during the foamingprocess and the contacting surfaces adhere to one another withsufficient adhesion to result in a unitary foam structure. The streamsof molten extrudate exiting the die take the form of strands orprofiles, which desirably foam, coalesce, and adhere to one another toform a unitary structure. Desirably, the coalesced individual strands orprofiles should remain adhered in a unitary structure to prevent stranddelamination under stresses encountered in preparing, shaping, and usingthe foam. Apparatuses and method for producing foam structures incoalesced strand form are seen in U.S. Pat. Nos. 3,573,152 and4,824,720, both of which are incorporated herein by reference.

The present foam structures may also be formed by an accumulatingextrusion process as seen in U.S. Pat. No. 4,323,528, which isincorporated by reference herein. In this process, low density foamstructures having large lateral cross-sectional areas are preparedby: 1) forming under pressure a gel of the compositions of the presentinvention and a blowing agent at a temperature at which the viscosity ofthe gel is sufficient to retain the blowing agent when the gel isallowed to expand; 2) extruding the gel into a holding zone maintainedat a temperature and pressure which does not allow the gel to foam, theholding zone having an outlet die defining an orifice opening into azone of lower pressure at which the gel foams, and an openable gateclosing the die orifice; 3) periodically opening the gate; 4)substantially concurrently applying mechanical pressure by a movable ramon the gel to eject it from the holding zone through the die orificeinto the zone of lower pressure, at a rate greater than that at whichsubstantial foaming in the die orifice occurs and less than that atwhich substantial irregularities in cross-sectional area or shapeoccurs; and 5) permitting the ejected gel to expand unrestrained in atleast one dimension to produce the foam structure.

The present foam structures may also be formed into foam beads suitablefor molding into articles by expansion of pre-expanded beads containinga blowing agent. The beads may be molded at the time of expansion toform articles of various shapes. Processes for making expanded beads andmolded expanded beam foam articles are described in Plastic Foams, PartII, Frisch And Saunders, pp. 544-585, Marcel Dekker, Inc. (1973) andPlastic Materials, Brydson, 5^(th) Ed., pp. 426-429, Butterworths(1989).

Expandable and expanded beads can be made by a batch or by an extrusionprocess. The batch process of making expandable beads is essentially thesame as for manufacturing expandable polystyrene (EPS). The granules ofa polymer blend, made either by melt blending or in-reactor blending,are impregnated with a blowing agent in an aqueous suspension or in ananhydrous state in a pressure vessel at an elevated temperature andpressure. The granules are then either rapidly discharged into a regionof reduced pressure to expand to foam beads or cooled and discharged asunexpanded beads. The unexpanded beads are then heated to expand with aproper means, e.g., with steam or with hot air. The extrusion method isessentially the same as the conventional foam extrusion process asdescribed above up to the die orifice. The die has multiple holes. Inorder to make unfoamed beads, the foamable strands exiting the dieorifice are immediately quenched in a cold water bath to prevent foamingand then pelletized. Or, the strands are converted to foam beads bycutting at the die face and then allowed to expand.

The foam beads may then be molded by any means known in the art, such ascharging the foam beads to the mold, compressing the mold to compressthe beads, and heating the beads such as with steam to effect coalescingand welding of the beads to form the article. Optionally, the beads maybe impregnated with air or other blowing agent at an elevated pressureand temperature prior to charging to the mold. Further, the beads may beheated prior to charging. The foam beads may then be molded to blocks orshaped articles by a suitable molding method known in the art. (Some ofthe methods are taught in U.S. Pat. Nos. 3,504,068 and 3,953,558.)Excellent teachings of the above processes and molding methods are seenin C.P. Park, supra, p. 191, pp. 197-198, and pp. 227-229, which areincorporated herein by reference.

To make the foam beads, blends of alkenyl aromatic polymers with one ormore substantially random interpolymer are formed into discrete resinparticles such as granulated resin pellets and are: suspended in aliquid medium in which they are substantially insoluble such as water;impregnated with a blowing agent by introducing the blowing agent intothe liquid medium at an elevated pressure and temperature in anautoclave or other pressure vessel; and rapidly discharged into theatmosphere or a region of reduced pressure to expand to form the foambeads. This process is well taught in U.S. Pat. Nos. 4,379,859 and4,464,484, which are incorporated herein by reference.

A process for making expandable thermoplastic beads comprises :providing an alkenyl aromatic monomer and optionally at least oneadditional monomer, which is different from, and polymerizable with saidalkenyl aromatic monomer; and dissolving in at least one of saidmonomers the substantially random interpolymers; polymerizing the firstand second monomers to form thermoplastic particles; incorporating ablowing agent into the thermoplastic particles during or afterpolymerization; and cooling the thermoplastic particles to formexpandable beads. The alkenyl aromatic monomer is present in an amountof at least about 50, preferably at least about 70, more preferably atleast about 90 wt % based on the combined weights of the polymerizeablemonomer(s).

Another process for making expandable thermoplastic beads comprises :heating the blends of alkenyl aromatic polymers with one or moresubstantially random interpolymers to form a melt polymer; incorporatinginto the melt polymer material at an elevated temperature a blowingagent to form a foamable gel; cooling the gel to an optimum temperaturewhich is one at which foaming will not occur, extruding through a diecontaining one or more orifices to form one or more essentiallycontinuous expandable thermoplastic strand(s); and pelletizing theexpandable thermoplastic strand(s) to form expandable thermoplasticbead(s). Alternatively expanded thermoplastic foam beads may be made if,prior to extruding from the die, the gel is cooled to an optimumtemperature which in this case is at or above the blends glasstransition temperature or melting point. For the expanded thermoplasticfoam beads of the present invention, the optimum foaming temperature isin a range sufficient to produce an open cell content in the foam of 20vol % or less.

The present foam structures may also be used to make foamed films forbottle labels and other containers using either a blown film or a castfilm extrusion process. The films may also be made by a co-extrusionprocess to obtain foam in the core with one or two surface layers, whichmay or may not be comprised of the polymer compositions used in thepresent invention.

Due to present environmental concerns over the use of potentiallyozone-depleting blowing agents, it is desirable to make alkenyl aromaticpolymer foams with blowing agents having reduced or zero ozone-depletionpotential. Such blowing agents include inorganic blowing agents such asnitrogen, sulfur hexafluoride (SF₆), and argon; organic blowing agentssuch as carbon dioxide and hydrofluorocarbons such as1,1,1,2-tetrafluoroethane (HFC-134a), difluoromethane (HFC-32),1,1-difluoroethane (HFC-152a), 1,1,2,2-tetrafluoroethane (HFC-134),1,1,1,3,3-pentafluoropropane, pentafluoroethane (HFC-125), fluoroethane(HFC-161) and 1,1,1-trifluoroethane (HFC-143a) and hydrocarbons such asmethane, ethane, propane, n-butane, isobutane, n-pentane, isopentane,cyclopentane and neopentane; and chemical blowing agents which includeazodicarbonamide, azodiisobutyro-nitrile, benzenesulfonhydrazide,4,4-oxybenzene sulfonyl-semicarbazide, p-toluene sulfonylsemi-carbazide, barium azodicarboxylate,N,N'-dimethyl-N,N'-dinitroso-terephthalamide, trihydrazino triazine andmixtures of citric acid and sodium bicarbonate such as the variousproducts sold under the name Hydrocerol™ (a product and trademark ofBoehringer Ingelheim). All of these blowing agents may be used as singlecomponents or any mixture of combination thereof, or in mixtures withother co-blowing agents.

The blowing agent(s), when mixed with a co-blowing agent, are present inan amount of 50 mole % or more, preferably 70 mole % or more (based onthe total g-moles of blowing agent and co-blowing agent).

Co-blowing agents useful with the blowing agents used in the presentinvention include inorganic co-blowing agents, organic co-blowing agentsand chemical co-blowing agents. Suitable inorganic co-blowing agentsinclude helium, water and air. Organic co-blowing agents includealiphatic alcohols including methanol, ethanol, n-propanol, andisopropanol. Fully and partially halogenated aliphatic hydrocarbonsinclude fluorocarbons, chlorocarbons, and chlorofluorocarbons. Examplesof fluorocarbons include methyl fluoride, perfluoromethane, ethylfluoride, perfluoroethane, 2,2-difluoropropane, 1,1,1-trifluoropropane,perfluoropropane, dichloropropane, difluoropropane, perfluorobutane,perfluorocyclobutane. Partially halogenated chlorocarbons andchlorofluorocarbons for use in this invention include methyl chloride,methylene chloride, ethyl chloride, 1,1,1-trichloro-ethane,1,1-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1,1-difluoroethane(HCFC-142b), chlorodifluoromethane (HCFC-22),1,1-dichloro-2,2,2-trifluoroethane (HCFC-123) and1-chloro-1,2,2,2-tetrafluoroethane (HCFC-124). Fully halogenatedchlorofluorocarbons include trichloromonofluoromethane (CFC-11),dichlorodifluoromethane (CFC-12), trichloro-trifluoroethane (CFC-113),dichlorotetrafluoroethane (CFC-114), chloroheptafluoropropane, anddichlorohexafluoropropane.

The total amount of blowing agents and co-blowing agents incorporatedinto the polymer melt material to make a foam-forming polymer gel isfrom about 0.2 to about 5.0 gram-moles per kilogram of polymer,preferably from about 0.5 to about 3.0 gram-moles per kilogram ofpolymer, and most preferably from about 1.0 to 2.5 gram-moles perkilogram of polymer.

In addition, a nucleating agent may be added in order to control thesize of foam cells. Preferred nucleating agents include inorganicsubstances such as calcium carbonate, talc, clay, silica, bariumstearate, diatomaceous earth, mixtures of citric acid and sodiumbicarbonate, and the like. The amount of nucleating agent employed mayrange from 0 to about 5 parts by weight per hundred parts by weight of apolymer resin. The preferred range is from 0 to about 3 parts by weight.

Various additives may be incorporated in the present foam structure suchas inorganic fillers, pigments, antioxidants, acid scavengers,ultraviolet absorbers, flame retardants, processing aids, extrusionaids, other thermoplastic polymers, antistatic agents, and the like.Examples of other thermoplastic polymers include alkenyl aromatichomopolymers or copolymers (having molecular weight of about 2,000 toabout 50,000) and ethylenic polymers.

The foam has a density of from about 10 to about 150 and most preferablyfrom about 10 to about 70 kilograms per cubic meter according to ASTMD-1622-88. The foam has an average cell size of from about 0.05 to about5.0 and preferably from about 0.1 to about 1.5 millimeters according toASTM D3576-77.

The present foam has an increase of cell size of about 5%, preferablyabout 10%, more preferably about 15% or more relative to an analogousfoam made without the substantially random interpolymer.

The present foam is particularly suited to be formed into a plank orsheet, desirably one having a cross-sectional area of 30 squarecentimeters (cm) or more and a thickness or minor dimension incross-section of 0.95 cm or more, preferably 2.5 cm or more.

The present foam is closed cell. The closed cell content of the presentfoams is greater than or equal to 80 percent according to ASTM D2856-94.

The present foam structures may be used to insulate a surface byapplying to the surface an insulating panel fashioned from the presentstructure, as used in for example, external wall sheathing (home thermalinsulation), foundation insulation, and residing underlayment. Suchpanels are useful in any conventional insulating applications such asroofing, buildings, refrigerators and the like. Other applicationsinclude floating docks and rafts (buoyancy applications) as well asvarious floral and craft applications.

Properties of the Intervolymers and Blend Compositions Used to Preparethe Foams of the Present Invention.

The polymer compositions used to prepare the foams of the presentinvention comprise from about 80 to about 99.7, preferably from about 80to about 99.5, more preferably from about 80 to about 99 wt %, (based onthe combined weights of substantially random interpolymer and thealkenyl aromatic homopolymers or copolymer) of one or more alkenylaromatic homopolymers or copolymers.

The molecular weight distribution (M_(w) /M_(n)) of the alkenyl aromatichomopolymers or copolymers used to prepare the foams having enlargedcell size of the present invention is from about 2 to about 7.

The molecular weight (Mw) of the alkenyl aromatic homopolymers orcopolymers used to prepare the foams having enlarged cell size of thepresent invention is from about 100,000 to about 500,000, preferablyfrom about 120,000 to about 350,000, more preferably 130,000 to 325,000.

The alkenyl aromatic polymer material used to prepare the foams of thepresent invention comprises greater than 50 and preferably greater than70 weight percent alkenyl aromatic monomeric units. Most preferably, thealkenyl aromatic polymer material is comprised entirely of alkenylaromatic monomeric units.

The polymer compositions used to prepare the foams of the presentinvention comprise from about 0.3 to about 20, preferably from about 0.5to about 20, more preferably from about 1 to about 20 wt %, (based onthe combined weights of substantially random interpolymer and thealkenyl aromatic homopolymers or copolymers) of one or moresubstantially random interpolymers.

These substantially random interpolymers used to prepare the foamshaving enlarged cell size of the present invention usually contain fromabout 8 to about 65, preferably from about 10 to about 45, morepreferably from about 13 to about 39 mole percent of at least one vinylor vinylidene aromatic monomer and/or aliphatic or cycloaliphatic vinylor vinylidene monomer and from about 35 to about 92, preferably fromabout 55 to about 90, more preferably from about 61 to about 87 molepercent of ethylene and/or at least one aliphatic (α-olefin having from3 to about 20 carbon atoms.

The melt index (I₂) of the substantially random interpolymers used toprepare the foams of the present invention is from about 0.01 to about1000, preferably of from about 0.3 to about 30, more preferably of fromabout 0.5 to about 10 g/10 min.

The molecular weight distribution (M_(w) /M_(n)) of the substantiallyrandom interpolymer used to prepare the foams having enlarged cell sizeof the present invention is from about 1.5 to about 20, preferably offrom about 1.8 to about 10, more preferably of from about 2 to about 5.

In addition, minor amounts of alkenyl aromatic homopolymers orcopolymers having a molecular weight of about 2,000 to about 50,000,preferably from about 4,000 to about 25,000 can be added in an amountnot exceeding about 20 wt % (based on the combined weights ofsubstantially random interpolymer and the various alkenyl aromatichomopolymers or copolymers).

The following examples are illustrative of the invention, but are not tobe construed as to limiting the scope thereof in any manner.

EXAMPLES

Test Methods

a) Melt Flow and Density Measurements

The molecular weight of the substantially random interpolymers used inthe present invention is conveniently indicated using a melt indexmeasurement according to ASTM D-1238, Condition 190° C./2.16 kg(formally known as "Condition (E)" and also known as I₂) was determined.Melt index is inversely proportional to the molecular weight of thepolymer. Thus, the higher the molecular weight, the lower the meltindex, although the relationship is not linear.

Also useful for indicating the molecular weight of the substantiallyrandom interpolymers used in the present invention is the Gottfert meltindex (G, cm³ /10 min) which is obtained in a similar fashion as formelt index (I₂) using the ASTM D1238 procedure for automatedplastometers, with the melt density set to 0.7632, the melt density ofpolyethylene at 190° C.

The relationship of melt density to styrene content for ethylene-styreneinterpolymers was measured, as a function of total styrene content, at190° C. for a range of 29.8% to 81.8% by weight styrene. Atacticpolystyrene levels in these samples was typically 10% or less. Theinfluence of the atactic polystyrene was assumed to be minimal becauseof the low levels. Also, the melt density of atactic polystyrene and themelt densities of the samples with high total styrene are very similar.The method used to determine the melt density employed a Gottfert meltindex machine with a melt density parameter set to 0.7632, and thecollection of melt strands as a function of time while the I₂ weight wasin force. The weight and time for each melt strand was recorded andnormalized to yield the mass in grams per 10 minutes. The instrument'scalculated I₂ melt index value was also recorded. The equation used tocalculate the actual melt density is

    δ=δ.sub.0.7632 xI.sub.2 /I.sub.2 Gottfert

where δ₀.7632 =0.7632 and I₂ Gottfert=displayed melt index.

A linear least squares fit of calculated melt density versus totalstyrene content leads to an equation with a correlation coefficient of0.91 for the following equation:

    δ=0.00299×S+0.723

where S=weight percentage of styrene in the polymer. The relationship oftotal styrene to melt density can be used to determine an actual meltindex value, using these equations if the styrene content is known. Sofor a polymer that is 73% total styrene content with a measured meltflow (the "Gottfert number"), the calculation becomes:

    x=0.00299*73+0.723=0.9412

where 0.9412/0.7632=I₂ /G# (measured)=1.23

b) Styrene Analyses

Interpolymer styrene content and atactic polystyrene concentration weredetermined using proton nuclear magnetic resonance (¹ H N.M.R). Allproton NMR samples were prepared in 1, 1, 2, 2-tetrachloroethane-d₂(TCE-d₂). The resulting solutions were 1.6-3.2 percent polymer byweight. Melt index (I2) was used as a guide for determining sampleconcentration. Thus when the I₂ was greater than 2 g/10 min, 40 mg ofinterpolymer was used; with an I₂ between 1.5 and 2 g/10 min, 30 mg ofinterpolymer was used; and when the I₂ was less than 1.5 g/10 min, 20 mgof interpolymer was used. The interpolymers were weighed directly into 5mm sample tubes. A 0.75 mL aliquot of TCE-d₂ was added by syringe andthe tube was capped with a tight-fitting polyethylene cap. The sampleswere heated in a water bath at 85° C. to soften the interpolymer. Toprovide mixing, the capped samples were occasionally brought to refluxusing a heat gun.

Proton NMR spectra were accumulated on a Varian VXR 300 with the sampleprobe at 80° C., and referenced to the residual protons of TCE-d₂ at5.99 ppm. The delay times were varied between 1 second, and data wascollected in triplicate on each sample. The following instrumentalconditions were used for analysis of the interpolymer samples:

Varian VXR-300, standard ¹ H:

Sweep Width, 5000 Hz

Acquisition Time, 3.002 sec

Pulse Width, 8 μsec

Frequency, 300 MHz

Delay, 1 sec

Transients, 16

The total analysis time per sample was about 10 minutes.

Initially, a ¹ H NMR spectrum for a sample of polystyrene, was acquiredwith a delay time of one second. The protons were "labeled": b, branch;a, alpha; o, ortho; m, meta; p, para, as shown in FIG. 1. ##STR6##

Integrals were measured around the protons labeled in FIG. 1; the 'A'designates aPS. Integral A₇.1, (aromatic, around 7.1 ppm) is believed tobe the three ortho/para protons; and integral A₆.6 (aromatic, around 6.6ppm) the two meta protons. The two aliphatic protons labeled a resonateat 1.5 ppm; and the single proton labeled b is at 1.9 ppm. The aliphaticregion was integrated from about 0.8 to 2.5 ppm and is referred to asA_(al). The theoretical ratio for A₇.1 : A₆.6 : A_(al) is 3: 2: 3, or1.5: 1: 1.5, and correlated very well with the observed ratios for thepolystyrene sample for several delay times of 1 second. The ratiocalculations used to check the integration and verify peak assignmentswere performed by dividing the appropriate integral by the integral A₆.6Ratio A_(r) is A₇.1 /A₆.6.

Region A₆.6 was assigned the value of 1. Ratio Al is integral A_(al)/A₆.6. All spectra collected have the expected 1.5: 1: 1.5 integrationratio of (o+p): m: (α+b). The ratio of aromatic to aliphatic protons is5 to 3. An aliphatic ratio of 2 to 1 is predicted based on the protonslabeled α and b respectively in FIG. 1. This ratio was also observedwhen the two aliphatic peaks were integrated separately.

For the ethylene/styrene interpolymers, the ¹ H NMR spectra using adelay time of one second, had integrals C₇.1, C₆.6, and C_(al) defined,such that the integration of the peak at 7.1 ppm included all thearomatic protons of the copolymer as well as the o & p protons of aPS.Likewise, integration of the aliphatic region C_(al) in the spectrum ofthe interpolymers included aliphatic protons from both the aPS and theinterpolymer with no clear baseline resolved signal from either polymer.The integral of the peak at 6.6 ppm C₆.6 is resolved from the otheraromatic signals and it is believed to be due solely to the aPShomopolymer (probably the meta protons). (The peak assignment foratactic polystyrene at 6.6 ppm (integral A₆.6) was made based uponcomparison to the authentic polystyrene sample). This is a reasonableassumption since, at very low levels of atactic polystyrene, only a veryweak signal is observed here. Therefore, the phenyl protons of thecopolymer must not contribute to this signal. With this assumption,integral A₆ 6 becomes the basis for quantitatively determining the aPScontent.

The following equations were then used to determine the degree ofstyrene incorporation in the ethylene/styrene interpolymer samples:

(C Phenyl)=C₇.1 +A₇.1 -(1.5×A₆.6)

(C Aliphatic)=C_(al) -(15×A₆.6)

S_(c) =(C Phenyl)/5

e_(c) =(C Aliphatic-(3×s_(c)))/4

E=e_(c) /(e_(c) +S_(c))

S_(c) =S_(c) /(e_(c) +s_(c))

and the following equations were used to calculate the mol % ethyleneand styrene in the interpolymers. ##EQU1## where: s_(c) and e_(c) arestyrene and ethylene proton fractions in the interpolymer, respectively,and S_(c) and E are mole fractions of styrene monomer and ethylenemonomer in the interpolymer, respectively.

The weight percent of aPS in the interpolymers was then determined bythe following equation: ##EQU2##

The total styrene content was also determined by quantitative FourierTransform Infrared spectroscopy (FTIR0.

Preparation of Ethylene/Styrene Interpolymers (ESI's) Used in Examplesand Comparative Experiments of Present Invention

Preparation of ESI #'s 1-2

ESI #'s 1-2 are substantially random ethylene/styrene interpolymersprepared using the following catalyst and polymerization procedures.

Preparation of Catalyst A(dimethyl[N-(1,1-dimethylethyl)-1,1-dimethyl-1-[(12,3,4,5-η-1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl]silanaminato(2)-N]-titanium)

Preparation of 3,5,6,7-Tetrahydro-s-Hydrindacen-1(2H)-one

Indan (94.00 g, 0.7954 moles) and 3-chloropropionyl chloride (100.99 g,0.7954 moles) were stirred in CH₂ Cl₂ (300 mL) at 0° C. as AlCl₃ (130.00g, 0.9750 moles) was added slowly under a nitrogen flow. The mixture wasthen allowed to stir at room temperature for 2 hours. The volatiles werethen removed. The mixture was then cooled to 0° C. and concentrated H₂SO₄ (500 mL) slowly added. The forming solid had to be frequently brokenup with a spatula as stirring was lost early in this step. The mixturewas then left under nitrogen overnight at room temperature. The mixturewas then heated until the temperature readings reached 90° C. Theseconditions were maintained for a 2 hour period of time during which aspatula was periodically used to stir the mixture. After the reactionperiod crushed ice was placed in the mixture and moved around. Themixture was then transferred to a beaker and washed intermittently withH₂ O and diethylether and then the fractions filtered and combined. Themixture was washed with H₂ O (2×200 mL). The organic layer was thenseparated and the volatiles removed. The desired product was thenisolated via recrystallization from hexane at 0° C. as pale yellowcrystals (22.36 g, 16.3% yield).

¹ H NMR (CDCl₃): d2.04-2.19 (m, 2 H), 2.65 (t, ³.sbsp.J HH=5.7 Hz, 2 H),2.84-3.0 (m, 4 H), 3.03 (t, ³.sbsp.J HH=5.5 Hz, 2 H), 7.26 (s, 1 H),7.53 (s, 1 H). ¹³ C NMR (CDCl₃): d25.71, 26.01, 32.19, 33.24, 36.93,118.90, 122.16, 135.88, 144.06, 152.89, 154.36, 206.50. GC-MS:Calculated for C₁₂ H₁₂ O 172.09, found 172.05.

2) Preparation of 1,2,3,5-Tetrahydro-7-phenyl-s-indacen.

3,5,6,7-Tetrahydro-s-Hydrindacen-1(2H)-one (12.00 g, 0.06967 moles) wasstirred in diethyl ether (200 mL) at 0° C. as PhMgBr (0.105 moles, 35.00mL of 3.0 M solution in diethyl ether) was added slowly. This mixturewas then allowed to stir overnight at room temperature. After thereaction period the mixture was quenched by pouring over ice. Themixture was then acidified (pH=1) with HCl and stirred vigorously for 2hours. The organic layer was then separated and washed with H₂ O (2×100mL) and then dried over MgSO₄. Filtration followed by the removal of thevolatiles resulted in the isolation of the desired product as a dark oil(14.68 g, 90.3% yield).

¹ H NMR (CDCl₃): d2.0-2.2 (m, 2 H), 2.8-3.1 (m, 4 H), 6.54 (s, 1H),7.2-7.6 (m, 7 H). GC-MS: Calculated for C₁₈ H₁₆ 232.13, found 232.05.

3) Preparation of 1,2,3,5-Tetrahydro-7-phenyl-s-indacene, dilithiumsalt.

1,2,3,5-Tetrahydro-7-phenyl-s-indacen (14.68 g, 0.06291 moles) wasstirred in hexane (150 mL) as nBuLi (0.080 moles, 40.00 mL of 2.0 Msolution in cyclohexane) was slowly added. This mixture was then allowedto stir overnight. After the reaction period the solid was collected viasuction filtration as a yellow solid which was washed with hexane, driedunder vacuum, and used without further purification or analysis (12.2075g, 81.1% yield).

4) Preparation ofChlorodimethyl(1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl)silane.

1,2,3,5-Tetrahydro-7-phenyl-s-indacene, dilithium salt (12.2075 g,0.05102 moles) in THF (50 mL) was added dropwise to a solution of Me₂SiCl₂ (19.5010 g, 0.1511 moles) in THF (100 mL) at 0° C. This mixturewas then allowed to stir at room temperature overnight. After thereaction period the volatiles were removed and the residue extracted andfiltered using hexane. The removal of the hexane resulted in theisolation of the desired product as a yellow oil (15.1492 g, 91.1%yield).

¹ H NMR (CDCl₃): d0.33 (s, 3 H), 0.38 (s, 3 H), 2.20 (p, ³.sbsp.J HH=7.5Hz, 2 H), 2.9-3.1(m, 4 H), 3.84 (s, 1 H), 6.69 (d, ^(3is) J HH=2.8 Hz, 1H), 7.3-7.6 (m, 7 H), 7.68 (d, ³.sbsp.J HH=7.4 Hz, 2 H). ¹³ C NMR(CDCl₃): d0.24, 0.38, 26.28, 33.05, 33.18, 46.13, 116.42, 119.71,127.51, 128.33, 128.64, 129.56, 136.51, 141.31, 141.86, 142.17, 142.41,144.62. GC-MS: Calculated for C₂₀ H₂₁ ClSi 324.11, found 324.05.

5) Preparation of N-(1,1-Dimethylethyl)-1,1-dimethyl-1-(1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl)silanamine.

Chlorodimethyl(1,5 ,6,7-tetrahydro-3-phenyl-s-indacen-1-yl)silane(10.8277 g, 0.03322 moles) was stirred in hexane (150 mL) as NEt₃(3.5123 g, 0.03471 moles) and t-butylamine (2.6074 g, 0.03565 moles)were added. This mixture was allowed to stir for 24 hours. After thereaction period the mixture was filtered and the volatiles removedresulting in the isolation of the desired product as a thick red-yellowoil (10.6551 g, 88.7% yield).

¹ H NMR (CDCl₃): d0.02 (s, 3 H), 0.04 (s, 3 H), 1.27 (s, 9 H), 2.16 (p,³.sbsp.J HH=7.2 Hz, 2 H), 2.9-3.0 (m, 4 H), 3.68 (s, 1 H), 6.69 (s, 1H), 7.3-7.5 (m, 4 H), 7.63 (d, ³.sbsp.J HH=7.4 Hz, 2 H). ¹³ C NMR(CDCl3): d-0.32, -0.09, 26.28, 33.39, 34.11, 46.46, 47.54, 49.81,115.80, 119.30, 126.92, 127.89, 128.46, 132.99, 137.30, 140.20, 140.81,141.64, 142.08, 144.83.

6) Preparation of N-(1,1-Dimethylethyl)-1,1-dimethyl-1-(1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl) silanamine, dilithium salt.

N-(1,1-Dimethylethyl)-1,1-dimethyl-1-(1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl)silanamine (10.6551 g, 0.02947moles) was stirred in hexane (100 mL) as nBuLi (0.070 moles, 35.00 mL of2.0 M solution in cyclohexane) was added slowly. This mixture was thenallowed to stir overnight during which time no salts crashed out of thedark red solution. After the reaction period the volatiles were removedand the residue quickly washed with hexane (2×50 mL). The dark redresidue was then pumped dry and used without further purification oranalysis (9.6517 g, 87.7% yield).

7) Preparation ofDichloro[N-(1,1-dimethylethyl)-1,1-dimethyl-1-[(1,2,3,4,5-η)-1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl]silanaminato(2-)-N]titanium

N-(1,1-Dimethylethyl)-1,1-dimethyl-1-(1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl)silanamine,dilithium salt (4.5355 g, 0.01214 moles) in THF (50 mL) was addeddropwise to a slurry of TiCl₃ (THF)₃ (4.5005 g, 0.01214 moles) in THF(100 mL). This mixture was allowed to stir for 2 hours. PbCl₂ (1.7136 g,0.006162 moles) was then added and the mixture allowed to stir for anadditional hour. After the reaction period the volatiles were removedand the residue extracted and filtered using toluene. Removal of thetoluene resulted in the isolation of a dark residue. This residue wasthen slurried in hexane and cooled to 0° C. The desired product was thenisolated via filtration as a red-brown crystalline solid (2.5280 g,43.5% yield).

¹ H NMR (CDCl₃): d0.71 (s, 3 H), 0.97 (s, 3 H), 1.37 (s, 9 H), 2.0-2.2(m, 2 H), 2.9-3.2 (m, 4 H), 6.62 (s, 1 H), 7.35-7.45 (m, 1 H), 7.50 (t,³.sbsp.J HH=7.8 Hz, 2 H), 7.57 (s, 1 H), 7.70 (d, ³.sbsp.J HH=7.1 Hz, 2H), 7.78 (s, 1 H).

¹ H NMR (C₆ D₆): d0.44 (s, 3 H), 0.68 (s, 3 H), 1.35 (s, 9 H), 1.6-1.9(m, 2 H),2.5-3.9 (m, 4 H), 6.65 (s, 1 H), 7.1-7.2 (m, 1 H), 7.24 (t,³.sbsp.J HH=7.1 Hz, 2 H), 7.61 (s, 1 H),7.69 (s, 1 H), 7.77-7.8 (m, 2H). ¹³ C NMR (CDCl₃): d1.29, 3.89, 26.47, 32.62, 32.84, 32.92, 63.16,98.25, 118.70, 121.75, 125.62, 128.46, 128.55, 128.79,129.01, 134.11,134.53, 136.04, 146.15, 148.93. ¹³ C NMR (C₆ D₆): d0.90,3.57,26.46,32.56,32.78, 62.88,98.14, 119.19, 121.97, 125.84, 127.15,128.83, 129.03, 129.55, 134.57, 135.04, 136.41, 136.51, 147.24, 148.96.

8) Preparation ofDimethyl[N-(1,1-dimethylethyl)-1,1-dimethyl-1-[(1,2,3,4,5-η)-1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl]silanaminato(2-)-N]titanium

Dichloro[N-(1,1-dimethylethyl)-1,1-dimethyl-1-[(1,2,3,4,5-η)1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl]silanaminato(2-)-N]titanium(0.4970 g, 0.001039 moles) was stirred in diethylether (50 mL) as MeMgBr(0.0021 moles, 0.70 mL of 3.0 M solution in diethylether) was addedslowly. This mixture was then stirred for I hour. After the reactionperiod the volatiles were removed and the residue extracted and filteredusing hexane. Removal of the hexane resulted in the isolation of thedesired product as a golden yellow solid (0.4546 g, 66.7% yield).

¹ H NMR (C₆ D₆): d0.071 (s, 3 H), 0.49 (s, 3 H), 0.70 (s, 3 H), 0.73 (s,3 H), 1.49 (s, 9 H), 1.7-1.8 (m, 2 H), 2.5-2.8 (m, 4 H), 6.41 (s, 1 H),7.29 (t, ³.sbsp.J HH=7.4 Hz, 2 H), 7.48 (s, 1 H), 7.72 (d, ³.sbsp.JHH=7.4 Hz, 2 H), 7.92 (s, 1 H). ¹³ C NMR (C₆ D₆): d2.19, 4.61, 27.12,32.86, 33.00, 34.73, 58.68, 58.82, 118.62, 121.98, 124.26, 127.32,128.63, 128.98, 131.23, 134.39, 136.38, 143.19, 144.85.

Polymerization for ESI #'s 1-2

ESI's 1-2 were prepared in a 6 gallon (22.7 L), oil jacketed, Autoclavecontinuously stirred tank reactor (CSTR). A magnetically coupledagitator with Lightning A-320 impellers provided the mixing. The reactorran liquid full at 475 psig (3,275 kPa). Process flow was in at thebottom and out of the top. A heat transfer oil was circulated throughthe jacket of the reactor to remove some of the heat of reaction. At theexit of the reactor was a micromotion flow meter that measured flow andsolution density. All lines on the exit of the reactor were traced with50 psi (344.7 kPa) steam and insulated.

Toluene solvent was supplied to the reactor at 30 psig (207 kPa). Thefeed to the reactor was measured by a Micro-Motion mass flow meter. Avariable speed diaphragm pump controlled the feed rate. At the dischargeof the solvent pump, a side stream was taken to provide flush flows forthe catalyst injection line (1 lb/hr (0.45 kg/hr)) and the reactoragitator (0.75 lb/hr (0.34 kg/hr)). These flows were measured bydifferential pressure flow meters and controlled by manual adjustment ofmicro-flow needle valves. Uninhibited styrene monomer was supplied tothe reactor at 30 psig (207 kpa). The feed to the reactor was measuredby a Micro-Motion mass flow meter. A variable speed diaphragm pumpcontrolled the feed rate. The styrene stream was mixed with theremaining solvent stream.

Ethylene was supplied to the reactor at 600 psig (4,137 kPa). Theethylene stream was measured by a Micro-Motion mass flow meter justprior to the Research valve controlling flow. A Brooks flowmeter/controller was used to deliver hydrogen into the ethylene streamat the outlet of the ethylene control valve. The ethylene/hydrogenmixture combines with the solvent/styrene stream at ambient temperature.The temperature of the solvent/monomer as it enters the reactor wasdropped to ˜5 ° C. by an exchanger with -5° C. glycol on the jacket.This stream entered the bottom of the reactor.

The three component catalyst system and its solvent flush also enteredthe reactor at the bottom but through a different port than the monomerstream. Preparation of the catalyst components took place in an inertatmosphere glove box. The diluted components were put in nitrogen paddedcylinders and charged to the catalyst run tanks in the process area.From these run tanks the catalyst was pressured up with piston pumps andthe flow was measured with Micro-Motion mass flow meters. These streamscombine with each other and the catalyst flush solvent just prior toentry through a single injection line into the reactor.

Polymerization was stopped with the addition of catalyst kill (watermixed with solvent) into the reactor product line after the micromotionflow meter measuring the solution density. Other polymer additives canbe added with the catalyst kill. A static mixer in the line provideddispersion of the catalyst kill and additives in the reactor effluentstream. This stream next entered post reactor heaters that provideadditional energy for the solvent removal flash. This flash occurred asthe effluent exited the post reactor heater and the pressure was droppedfrom 475 psig (3,275 kPa) down to ˜250 mm of pressure absolute at thereactor pressure control valve. This flashed polymer entered a hot oiljacketed devolatilizer. Approximately 85 percent of the volatiles wereremoved from the polymer in the devolatilizer. The volatiles exited thetop of the devolatilizer. The stream was condensed with a glycoljacketed exchanger and entered the suction of a vacuum pump and wasdischarged to a glycol jacket solvent and styrene/ethylene separationvessel. Solvent and styrene were removed from the bottom of the vesseland ethylene from the top. The ethylene stream was measured with aMicro-Motion mass flow meter and analyzed for composition. Themeasurement of vented ethylene plus a calculation of the dissolvedgasses in the solvent/styrene stream were used to calculate the ethyleneconversion. The polymer separated in the devolatilizer was pumped outwith a gear pump to a ZSK-30 devolatilizing vacuum extruder. The drypolymer exits the extruder as a single strand. This strand was cooled asit was pulled through a water bath. The excess water was blown from thestrand with air and the strand was chopped into pellets with a strandchopper.

Preparation of ESI #3

ESI 3 is a substantially random ethylene/styrene interpolymer preparedusing the following catalyst and polymerization procedures.

Preparation of CatalystB;(1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamido)-silanetitanium1,4-diphenylbutadiene)

1) Preparation of lithium 1H-cyclopenta[1]phenanthrene-2-yl

To a 250 ml round bottom flask containing 1.42 g (0.00657 mole) of1H-cyclopenta[1]phenanthrene and 120 ml of benzene was added dropwise,4.2 ml of a 1.60 M solution of n-BuLi in mixed hexanes. The solution wasallowed to stir overnight. The lithium salt was isolated by filtration,washing twice with 25 ml benzene and drying under vacuum. Isolated yieldwas 1.426 g (97.7 percent). 1H NMR analysis indicated the predominantisomer was substituted at the 2 position.

2) Preparation of(1H-cyclopenta[1]phenanthrene-2-yl)dimethylchlorosilane

To a 500 ml round bottom flask containing 4.16 g (0.0322 mole) ofdimethyldichlorosilane (Me₂ SiCl₂) and 250 ml of tetrahydrofuran (THF)was added dropwise a solution of 1.45 g (0.0064 mole) of lithium1H-cyclopenta[1]phenanthrene-2-yl in THF. The solution was stirred forapproximately 16 hours, after which the solvent was removed underreduced pressure, leaving an oily solid which was extracted withtoluene, filtered through diatomaceous earth filter aid (Celite™),washed twice with toluene and dried under reduced pressure. Isolatedyield was 1.98 g (99.5 percent).

3. Preparation of(1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamino)silane

To a 500 ml round bottom flask containing 1.98 g (0.0064 mole) of(1H-cyclopenta[1]phenanthrene-2-yl)dimethylchlorosilane and 250 ml ofhexane was added 2.00 ml (0.0160 mole) of t-butylamine. The reactionmixture was allowed to stir for several days, then filtered usingdiatomaceous earth filter aid (Celite™), washed twice with hexane. Theproduct was isolated by removing residual solvent under reducedpressure. The isolated yield was 1.98 g (88.9 percent).

4. Preparation of dilithio (1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamido)silane

To a 250 ml round bottom flask containing 1.03 g (0.0030 mole) of(1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamino)silane) and 120ml of benzene was added dropwise 3.90 ml of a solution of 1.6 M n-BuLiin mixed hexanes. The reaction mixture was stirred for approximately 16hours. The product was isolated by filtration, washed twice with benzeneand dried under reduced pressure. Isolated yield was 1.08 g (100percent).

5. Preparation of (1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamido)silanetitaniumdichloride

To a 250 ml round bottom flask containing 1.17 g (0.0030 mole) of TiCl₃•3THF and about 120 ml of THF was added at a fast drip rate about 50 mlof a THF solution of 1.08 g of dilithio(1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamido)silane. Themixture was stirred at about 20° C. for 1.5 h at which time 0.55 gm(0.002 mole) of solid PbCl₂ was added. After stirring for an additional1.5 h the THF was removed under vacuum and the reside was extracted withtoluene, filtered and dried under reduced pressure to give an orangesolid. Yield was 1.31 g (93.5 percent).

6. Preparation of(1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamido) silanetitanium1,4-diphenylbutadiene

To a slurry of(1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamido)silanetitaniumdichloride (3.48 g, 0.0075 mole) and 1.551 gm (0.0075 mole) of1,4-diphenyllbutadiene in about 80 ml of toluene at 70° C. was add 9.9ml of a 1.6 M solution of n-BuLi (0.0150 mole). The solution immediatelydarkened. The temperature was increased to bring the mixture to refluxand the mixture was maintained at that temperature for 2 hrs. Themixture was cooled to about -20° C. and the volatiles were removed underreduced pressure. The residue was slurried in 60 ml of mixed hexanes atabout 20° C. for approximately 16 hours. The mixture was cooled to about-25° C. for about 1 h. The solids were collected on a glass frit byvacuum filtration and dried under reduced pressure. The dried solid wasplaced in a glass fiber thimble and solid extracted continuously withhexanes using a soxhlet extractor. After 6 h a crystalline solid wasobserved in the boiling pot. The mixture was cooled to about -20° C.,isolated by filtration from the cold mixture and dried under reducedpressure to give 1.62 g of a dark crystalline solid. The filtrate wasdiscarded. The solids in the extractor were stirred and the extractioncontinued with an additional quantity of mixed hexanes to give anadditional 0.46 gm of the desired product as a dark crystalline solid.

Polymerization for ESI 3

ESI 3 was prepared in a continuously operating loop reactor (36.8 gal.139 L). An Ingersoll-Dresser twin screw pump provided the mixing. Thereactor ran liquid full at 475 psig (3,275 kPa) with a residence time ofapproximately 25 minutes. Raw materials and catalyst/cocatalyst flowswere fed into the suction of the twin screw pump through injectors andKenics static mixers. The twin screw pump discharged into a 2" diameterline which supplied two Chemineer-Kenics 10-68 Type BEM Multi-Tube heatexchangers in series. The tubes of these exchangers contained twistedtapes to increase heat transfer. Upon exiting the last exchanger, loopflow returned through the injectors and static mixers to the suction ofthe pump. Heat transfer oil was circulated through the exchangers jacketto control the loop temperature probe located just prior to the firstexchanger. The exit stream of the loop reactor was taken off between thetwo exchangers. The flow and solution density of the exit stream wasmeasured by a MicroMotion.

Solvent feed to the reactor was supplied by two different sources. Afresh stream of toluene from an 8480-S-E Pulsafeeder diaphragm pump withrates measured by a MicroMotion flowmeter was used to provide flush flowfor the reactor seals (20 lb/hr (9.1 kg/hr). Recycle solvent was mixedwith uninhibited styrene monomer on the suction side of five 8480-S-EPulsafeeder diaphragm pumps in parallel. These five Pulsafeeder pumpssupplied solvent and styrene to the reactor at 650 psig (4,583 kPa).Fresh styrene flow was measured by a MicroMotion flowmeter, and totalrecycle solvent/styrene flow was measured by a separate MicroMotionflowmeter. Ethylene was supplied to the reactor at 687 psig (4,838 kPa).The ethylene stream was measured by a Micro-Motion mass flowmeter. ABrooks flowmeter/controller was used to deliver hydrogen into theethylene stream at the outlet of the ethylene control valve.

The ethylene/hydrogen mixture combined with the solvent/styrene streamat ambient temperature. The temperature of the entire feed stream as itentered the reactor loop was lowered to 2° C. by an exchanger with -10°C. glycol on the jacket. Preparation of the three catalyst componentstook place in three separate tanks: fresh solvent and concentratedcatalyst/cocatalyst premix were added and mixed into their respectiverun tanks and fed into the reactor via variable speed 680-S-AEN7Pulsafeeder diaphragm pumps. As previously explained, the threecomponent catalyst system entered the reactor loop through an injectorand static mixer into the suction side of the twin screw pump. The rawmaterial feed stream was also fed into the reactor loop through aninjector and static mixer downstream of the catalyst injection point butupstream of the twin screw pump suction.

Polymerization was stopped with the addition of catalyst kill (watermixed with solvent) into the reactor product line after the Micro Motionflowmeter measuring the solution density. A static mixer in the lineprovided dispersion of the catalyst kill and additives in the reactoreffluent stream. This stream next entered post reactor heaters thatprovided additional energy for the solvent removal flash. This flashoccurred as the effluent exited the post reactor heater and the pressurewas dropped from 475 psig (3,275 kPa) down to 450 mmHg (60 kPa) ofabsolute pressure at the reactor pressure control valve.

This flashed polymer entered the first of two hot oil jacketeddevolatilizers. The volatiles flashing from the first devolatizer werecondensed with a glycol jacketed exchanger, passed through the suctionof a vacuum pump, and were discharged to the solvent andstyrene/ethylene separation vessel. Solvent and styrene were removedfrom the bottom of this vessel as recycle solvent while ethyleneexhausted from the top. The ethylene stream was measured with aMicroMotion mass flowmeter. The measurement of vented ethylene plus acalculation of the dissolved gases in the solvent/styrene stream wereused to calculate the ethylene conversion. The polymer and remainingsolvent separated in the devolatilizer was pumped with a gear pump to asecond devolatizer. The pressure in the second devolatizer was operatedat 5 mm Hg (0.7 kPa) absolute pressure to flash the remaining solvent.This solvent was condensed in a glycol heat exchanger, pumped throughanother vacuum pump, and exported to a 5 waste tank for disposal. Thedry polymer (<1000 ppm total volatiles) was pumped with a gear pump toan underwater pelletizer with 6-hole die, pelletized, spin-dried, andcollected in 1000 lb boxes.

The various catalysts, co-catalysts and process conditions used toprepare the various individual ethylene styrene interpolymers (ESI #'s1-3) are summarized in Table 1 and their properties are summarized inTable 2.

                                      TABLE 1                                     __________________________________________________________________________    Preparation Conditions for ESI #'s 1-3                                           Reactor                                                                           Solvent                                                                           Ethylene                                                                           Hydrogen                                                                           Styrene                                                                           Ethylene                                               ESI Temp Flow Flow Flow Flow Conversion B/Ti MMAO                                                                       .sup.d /Ti Co-                      # ° C. lb/hr lb/hr sccm lb/hr % Ratio Ratio Catalyst Catalyst        __________________________________________________________________________    ESI 1                                                                            93.0                                                                              37.9                                                                              3.1  13.5 6.9 96.2  2.99                                                                             7.0   A.sup.a                                                                           C.sup.c                             ESI 2 79.0 31.3 1.74 4.3 13.5 95.1 3.51 9.0 A.sup.a C.sup.c                   ESI-3 61 386 20 0 100 88 3.50 2.5 B.sup.b C.sup.c                           __________________________________________________________________________     *N/A = not available                                                          .sup.a Catalyst A is                                                          dimethyl[N(1,1-dimethylethyl)-1,1-dimethyl-1-[(1,2,3,4,5η)1,5,6,7-tet    ahydro-3-phenyl-s-indacen-1-yl]silanaminato(2)-Ntitanium.                      .sup.b Catalyst B is                                                          ;(1Hcyclopenta[1]phenanthrene2-yl)dimethyl(t-butylamido)-silanetitanium       1,4diphenylbutadiene)                                                         .sup.c Cocatalyst C is tris(pentafluorophenyl)borane, (CAS# 00110915-5),.     .sup.d a modified methylaluminoxane commercialy available from Akzo Nobel     as MMAO3A (CAS# 14690579-5)                                              

                  TABLE 2                                                         ______________________________________                                        Properties of ESI #'s 1-3                                                                                       Melt                                              Index,                                                                     wt. % mol. %  12 GottfertMelt                                                 Copolymer Copolymer  (g/10 Index                                             ESI # Styrene Styrene aPS wt % min) (cm3/10 min)                            ______________________________________                                        ESI-1                                                                              47.4      19.5      0.5          1.54                                      ESI-2 69.0 37.5 1.6  1.36                                                     ESI-3 69.5 38.0 8.9 0.94                                                    ______________________________________                                    

Polystyrene Blend Components

PS 1 is a granular polystyrene having a weight average molecular weight,Mw, of about

192,000 and a polydispersity, M_(w) /M_(n), of about 2.

PS 2 is a granular polystyrene having a weight average molecular weight,Mw, of about

145,000 and a polydispersity, M_(w) /M_(n), of about 6.

PS 3 is a granular polystyrene having a weight average molecular weight,Mw, of about 132,000 and a polydispersity, M_(w) /M_(n), of about 2.

Examples 1 and 2 Enlarged Cell Sizes With PS/ESI Blends, Using IsobutaneAs Blowing Agent

A foaming process comprising a single-screw extruder, mixer, coolers anddie was used to make foam. Isobutane was used as the blowing agent at aloading of 7.5 part-per-hundred-resin (phr) to foam polystyrene (PS) andPS/ESI blends.

                  TABLE 3                                                         ______________________________________                                        Enlarged Cell Sizes With PS/ESI Blends, Using Isobutane As                      Blowing Agent                                                                         Blend      foaming                                                                              foam density                                                                          open cells                                                                           cell size                            Ex # Composition temp °C. (kg/m.sup.3) (vol %) mm                    ______________________________________                                        Ex 1  80% PS1/20%                                                                              122      39.4    10.4   0.065                                   ESI 1                                                                        Ex 2 80% PS1/20% 117 48.1 1.2 0.068                                            ESI 2                                                                        Comp 100 wt % PS 1 127 52.1 0.8 0.048                                         Expt 1                                                                      ______________________________________                                    

Example 3 Enlarged Cell Sizes with PS/ESI Blends, Using CO₂ as BlowingAgent

A foaming process comprising a single-screw extruder, mixer, coolers anddie was used to make foam planks. Carbon dioxide (CO₂) was used as theblowing agent at a level of 4.7 phr to foam polystyrene and a blend ofpolystyrene with ESI. The other additives were: hexabromocyclododecane=2.5 phr; barium stearate =0.2 phr; blue pigment=0.15 phr;tetrasodiumpyrophosphate =0.2 phr; linear low density polyethylene=0.4phr.

                                      TABLE 4                                     __________________________________________________________________________    Enlarged cell sizes with PS/ESI blends, using CO.sub.2 as blowing agent           Blend Composition                                                                       foam temp                                                                          thickness                                                                          foam density                                                                        % open                                                                            av cell size                                  Ex # (wt %) ° C. mm kg/m.sup.3 cells mm WD %                         __________________________________________________________________________    Ex 3                                                                              95% PS2/5% ESI 3                                                                        123  37   40.9  18.8                                                                              0.34  1.9                                     Comp 2 100% PS2 123 48 37.9 4.1 0.28 1.3                                      Comp 3 100% PS3 125 25 41.0 3.2 0.23 1.2                                      Comp 4 98% PS3 + 2% GMS 121 25 37.7 7.2 0.30 13.1                           __________________________________________________________________________

The Examples and Comparative Examples of Tables 3 and 4 demonstrate thatfoams made from blends of polystyrene with substantially randomethylene/styrene interpolymers (using non-ozone depleting blowingagents) have enlarged cell size and closed cell structure (greater thanor equal to 80 vol % closed cell). In addition, Table 4 shows that thepresence of substantially random ethylene/styrene interpolymers in thefoams does not have a deleterious effect on creep under load at 80° C.(WD-DIN 18164), whereas use of the cell size enlarger, glycerol monostearate (GMS), had an adverse effect on WD.

What is claimed is:
 1. A process for making a closed cell alkenylaromatic polymer foam having enlarged cell size, which processcomprises;(I) forming a melt polymer material comprising;(A) from about80 to about 99.7 percent by weight (based on the combined weight ofComponents A and B) of one or more alkenyl aromatic polymers, andwherein at least one of said alkenyl aromatic polymers has a molecularweight (M_(w)) of from about 100,000 to about 500,000; and (B) fromabout 0.3 to about 20 percent by weight (based on the combined weight ofComponents A and B) of one or more substantially random interpolymershaving an I₂ of about 0.01 to about 1000 g/10 min, an M_(w) /M_(n) ofabout 1.5 to about 20; comprising(1) from about 8 to about 65 mol % ofpolymer units derived from;(a) at least one vinyl or vinylidene aromaticmonomer, or (b) at least one hindered aliphatic or cycloaliphatic vinylor vinylidene monomer, or (c) a combination of at least one aromaticvinyl or vinylidene monomer and at least one hindered aliphatic orcycloaliphatic vinyl or vinylidene monomer, and (2) from about 35 toabout 92 mol % of polymer units derived from at least one of ethyleneand/or a C₃₋₂₀ α-olefin; and (3) from 0 to about 20 mol % of polymerunits derived from one or more of ethylenically unsaturatedpolymerizable monomers other than those derived from (1) and (2); and,(C) optionally one or more nucleating agents and (D) optionally one ormore other additives; and (II) incorporating into said melt polymermaterial at an elevated pressure to form a foamable gel(E) one or moreblowing agents having zero ozone depletion potential and optionally oneor more co-blowing agents, and present in a total amount of from about0.2 to about 5.0 g moles per kg (based on the combined weight ofComponents A and B); (III) cooling said foamable gel to an optimumtemperature; and (IV) extruding the gel from step III through a die to aregion of lower pressure to form a foam; whereinas a result of saidprocess, the cell size of said foam is increased about 5 percent or morerelative to a corresponding foam without the substantially randominterpolymer.
 2. The process of claim 1, wherein said foam has athickness of about 0.95 cm or more and whereinA) in Component A, said atleast one alkenyl aromatic polymer has greater than 50 percent by weightalkenyl aromatic monomeric units, and has a molecular weight (M_(w)) offrom about 120,000 to about 350,000 and is present in an amount of fromabout 80 to about 99.5 percent by weight (based on the combined weightof Components A and B); B) said substantially random interpolymer,Component (B), has an I₂ of about 0.3 to about 30 g/10 min and an M_(w)/M_(n) of about 1.8 to about 10; is present in an amount of from about0.5 to about 20 percent by weight (based on the combined weight ofComponents A and B); and comprises(1) from about 10 to about 45 mol % ofpolymer units derived from;(a) said vinyl or vinylidene aromatic monomerrepresented by the following formula; ##STR7## wherein R¹ is selectedfrom the group of radicals consisting of hydrogen and alkyl radicalscontaining three carbons or less, and Ar is a phenyl group or a phenylgroup substituted with from 1 to 5 substituents selected from the groupconsisting of halo, C₁₋₄ -alkyl, and C₁₋₄ -haloalkyl; or (b) saidsterically hindered aliphatic or cycloaliphatic vinyl or vinylidenemonomer is represented by the following general formula; ##STR8##wherein A¹ is a sterically bulky, aliphatic or cycloaliphaticsubstituent of up to 20 carbons, R¹ is selected from the group ofradicals consisting of hydrogen and alkyl radicals containing from 1 toabout 4 carbon atoms, preferably hydrogen or methyl; each R² isindependently selected from the group of radicals consisting of hydrogenand alkyl radicals containing from 1 to about 4 carbon atoms, preferablyhydrogen or methyl; or alternatively R¹ and A¹ together form a ringsystem; or c) a combination of a and b; and (2) from about 55 to about90 mol % of polymer units derived from ethylene and/or said α-olefinwhich comprises at least one of propylene, 4-methyl-1-pentene, butene-1,hexene-1 or octene-1; and (3) said ethylenically unsaturatedpolymerizable monomers other than those derived from (1) and (2)comprises norbornene, or a C₁₋₁₀ alkyl or C₆₋₁₀ aryl substitutednorbornene; and (C) said nucleating agent, if present, Component (C),comprises one or more of calcium carbonate, talc, clay, silica, bariumstearate, diatomaceous earth, mixtures of citric acid and sodiumbicarbonate; and (D) said additive if present, Component (D), comprisesone or more of inorganic fillers, pigments, antioxidants, acidscavengers, ultraviolet absorbers, flame retardants, processing aids,other thermoplastic polymers, antistatic agents and extrusion aids; (E)said blowing agent, Component (E), is present in a total amount of fromabout 0.5 to about 3.0 moles/kg (based on the combined weight ofComponents A and B), and comprises 50% or more of one or more ofinorganic blowing agents, carbon dioxide, hydrofluorocarbons,hydrocarbons, or chemical blowing agents; andwherein the cell size ofsaid foam is enlarged about 10 percent or more relative to acorresponding foam without the substantially random interpolymer.
 3. Theprocess of claim 1, wherein said foam has a thickness of about 2.5 cm ormore and wherein;(A) in Component A, said at least one alkenyl aromaticpolymer has greater than 70 percent by weight alkenyl aromatic monomericunits, has a molecular weight (M_(w)) of from about 130,000 to about325,000 and a molecular weight distribution, (M_(w) /M_(n)) of fromabout 2 to about 7, and is present in an amount of from about 80 toabout 99 percent by weight (based on the combined weight of Components Aand B); (B) said substantially random interpolymer, Component (B), hasan I₂ of about 0.5 to about 10 g 10 min and an M_(w) /M_(n) from about 2to about 5, is present in an amount from about 1 to about 20 wt % (basedon the combined weight of Components A and B) and comprises(1) fromabout 13 to about 39 mol % of polymer units derived from;a) said vinylaromatic monomer which comprises styrene, (α-methyl styrene, ortho-,meta-, and para-methylstyrene, and the ring halogenated styrenes, or b)said aliphatic or cycloaliphatic vinyl or vinylidene monomers whichcomprises 5-ethylidene-2-norbornene or 1-vinylcyclo-hexene,3-vinylcyclo-hexene, and 4-vinylcyclohexene; or c) a combination of aand b; and (2) from about 61 to about 87 mol % of polymer units derivedfrom ethylene, or ethylene and said α-olefin, which comprises ethylene,or ethylene and at least one of propylene, 4-methyl-1-pentene, butene-1,hexene-1 or octene-1; and (3) said ethylenically unsaturatedpolymerizable monomers other than those derived from (1) and (2) isnorbornene; and (C) said nucleating agent, if present, Component (C),comprises one or more of talc, and mixtures of citric acid and sodiumbicarbonate; (D) said additive, if present, Component (D), comprises oneor more of carbon black, titanium dioxide, graphite, other thermoplasticpolymers, and flame retardants; and (E) said blowing agent, Component(E), is present in a total amount of from about 1.0 to about 2.5 g molesper kg (based on the combined weight of Components A and B) andcomprises 70% or more of one or more of, nitrogen, sulfur hexafluoride(SF₆), argon, carbon dioxide, 1,1,1,2-tetrafluoroethane (HFC-134a),difluoromethane (HFC-32), 1,1-difluoroethane (HFC-152a),1,1,2,2-tetrafluoroethane (HFC-134), 1,1,1,3,3-pentafluoropropane,pentafluoroethane (HFC-125), fluoroethane (HFC-161) and1,1,1-trifluoroethane (HFC-143a), methane, ethane, propane, n-butane,isobutane, n-pentane, isopentane, cyclopentane and neopentane,azodicarbonamide, azodiisobutyro-nitrile, benzenesulfonylhydrazide,4,4-oxybenzene sulfonyl-semicarbazide, p-toluene sulfonylsemi-carbazide, barium azodicarboxylate,N,N'-dimethyl-N,N'-dinitrosoterephthalamide, trihydrazino triazine andmixtures of citric acid and sodium bicarbonate; andwherein the cell sizeof said foam is enlarged about 15 percent or more relative to acorresponding foam without the substantially random interpolymer.
 4. Theprocess of claim 3, wherein in said alkenyl aromatic polymer, Component(A), is polystyrene, Component B is an ethylene/styrene copolymer, andthe blowing agent, Component (E), is one or more of propane, n-pentane,isobutane, carbon dioxide, 1,1,1,2-tetrafluoroethane (HFC-134a), or1,1,2,2-tetrafluoroethane (HFC-134).
 5. The process of claim 3, whereinsaid alkenyl aromatic polymer, Component (A), is polystyrene, in saidsubstantially random interpolymer Component B1(a) is styrene; andComponent B2 is ethylene and at least one of propylene,4-methyl-1-pentene, butene-1, hexene-1 or octene-1, and the blowingagent, Component (E), is one or more of propane, n-pentane, isobutane,carbon dioxide, 1,1,1,2-tetrafluoroethane (HFC-134a), or1,1,2,2-tetrafluoroethane (HFC-134).
 6. The process of claim 1, whereinthe foam has a density of from about 10 to about 150 kilograms per cubicmeter (kg/m3) and a cell size of about 0.05 to about 5.0 millimeters. 7.The process of claim 1, wherein the foam has a density of from about 10to about 70 kg/m3 and a cell size of about 0.1 to about 1.5 millimeters.8. The process of claim 1, wherein Component A comprises greater than 70percent by weight of alkenyl aromatic monomeric units, saidsubstantially random interpolymer is incorporated to increase the cellsize about 15 percent or more relative to a corresponding foam withoutthe substantially random interpolymer, and the foam has a density offrom about 10 to about 150 kg/m3 and a cell size of about 0.05 to about5.0 millimeters.
 9. The process of claim 1, wherein Component Acomprises greater than 70 percent by weight of alkenyl aromaticmonomeric units, the substantially random interpolymer is incorporatedto increase the cell size about 15 percent or more relative to acorresponding foam without the substantially random interpolymer, andthe foam has a density of from about 10 to about 70 kg/m³ and a cellsize of about 0.1 to about 1.5 millimeters.
 10. The process of claim 1wherein in step (IV) said foamable gel is extruded through amulti-orifice die to a region of lower pressure such that contactbetween adjacent streams of the molten extrudate occurs during thefoaming process and the contacting surfaces adhere to one another withsufficient adhesion to result in a unitary foam structure to form acoalesced strand foam.
 11. The process of claim 1 wherein in step (IV)said foamable gel is;1) extruded into a holding zone maintained at atemperature and pressure which does not allow the gel to foam, theholding zone having an outlet die defining an orifice opening into azone of lower pressure at which the gel foams, and an openable gateclosing the die orifice;2) periodically opening the gate;3)substantially concurrently applying mechanical pressure by a movable ramon the gel to eject it from the holding zone through the die orificeinto the zone of lower pressure, at a rate greater than that at whichsubstantial foaming in the die orifice occurs and less than that atwhich substantial irregularities in cross-sectional area or shapeoccurs; and 4) permitting the ejected gel to expand unrestrained in atleast one dimension to produce the foam structure.
 12. The process ofclaim 1 wherein the foamable gel from step (II) is cooled to an optimumtemperature at which foaming does not occur and then extruded through adie to form an essentially continuous expandable thermoplastic strandwhich is pelletized to form expandable thermoplastic beads.
 13. Theprocess of claim 1 wherein in step (IV) said foamable gel is extrudedthrough a die to form essentially continuous expanded thermoplasticstrands which are converted to foam beads by cutting at the die face andthen allowed to expand.